// Problem: 
// Contest: 
// URL: 
// Memory Limit: 
// Time Limit: 
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include<bits/stdc++.h>
using namespace std;
#define int long long
inline int read(){
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
bool judge(int x)
{
	vector<int> v;
	while(x)
	{
		v.push_back(x%10);
		x/=10;
	}
	int n=v.size();
	if(n%2==1)return 0;
	else
	{
		int a=0,b=0;
		for(int i=0;i<n/2;i++)
		{
			a+=v[i];
			b+=v[i+n/2];
		}
		return a==b;
	}
}
signed main()
{
	int t=1;
//	cin>>t;
	while(t--)
	{
		int n=100000000,ans=0;
		for(int i=1;i<=n;i++)
			if(judge(i))ans++;
		cout<<ans;
	}
	return 0;
}
